Caffeine and nootropic timing

What caffeine does, when it costs you sleep, and where the evidence for the rest runs thin.

1. Caffeine for the hard hours, early.

   A review found low to moderate amounts of caffeine improved alertness, attention and reaction time, with less consistent effects on memory and judgment (McLellan, Caldwell and Lieberman, 2016).¹

2. Daily drinker: the first cup is a reset, not a lift.

   In regular drinkers, caffeine mostly reversed the dip from overnight withdrawal; tolerance meant it did not raise mental alertness beyond that, though it did speed reaction time (Rogers et al., 2013).²

3. Caffeine with L-theanine: studied, modest, short-term.

   A meta-analysis of 11 placebo-controlled studies of tea compounds found moderate effects of the pair on self-rated alertness and attention switching in the first two hours, with a trend pointing to the caffeine more than the L-theanine (Camfield et al., 2014).³

4. Last cup nine hours before bed.

   Across 24 studies, caffeine cut total sleep by 45 minutes and deep sleep by about 11 on average; to avoid lost sleep, the authors put a cup of coffee at least 8.8 hours before bed, a pre-workout serve 13.2 (Gardiner et al., 2023).⁴

5. Sleeping fine is not proof.

   In a 12-person trial, a substantial dose six hours before bed cut measured sleep by more than an hour; sleep diaries showed a smaller loss that was not statistically significant (Drake et al., 2013).⁵

6. No espresso after dinner.

   In a five-person lab study, the caffeine in a double espresso three hours before bed pushed the melatonin rhythm about 40 minutes later, nearly half the shift from three hours of bright evening light (Burke et al., 2015).⁶

7. Other smart drugs: thin evidence.

   A review of the most popular smart drugs, mostly stimulants, found their benefit in healthy people uncertain, any reported gain temporary, and harms possible (Schifano et al., 2022).⁷

The first cup is yours. The rest, handled at your house.